London-listed Rainbow Rare Earths has appointed Australian State-owned mineral sciences and services company ANSTO Minerals to advance the flow sheet process optimisation at the Phalaborwa rare earths project, in South Africa.

The completion of ANSTO's project, after which Rainbow will publish a preliminary economic assessment (PEA) or scoping study, is expected to place the company in a strong position to fast-track the project at Phalaborwa, says Rainbow Rare Earths CEO George Bennett.

ANSTO has been engaged to perform scouting leach tests on drill samples from Phalaborwa to confirm the metallurgical variability within the gypsum stacks.

Metallurgical test work will then be carried out to produce an optimised process flow sheet for the PEA or scoping study, based on the original petrochemicals multinational Sasol bankable feasibility study-level flow sheet, which produced 3 t of cerium-depleted mixed rare earth carbonate directly from the gypsum.

Phalaborwa's flow sheet is expected to be significantly simpler than those required for other rare earths projects around the world, as the rare earths exist in a cracked chemical form within the two gypsum stacks, obviating the need for the costly and capital-intensive stages of first producing a concentrate and then cracking it prior to beneficiation.

"Phalaborwa does not require waste stripping, hard-rock mining, significant crushing or milling. The project also has the capacity to progress straight to the downstream production of a mixed rare earth carbonate owing to the 'cracked' nature of the rare earths within the gypsum, which eliminates various processing stages that would normally be required in the production of a mixed rare earth carbonate. We believe Phalaborwa has the potential to be one of the lowest capital intensity projects in the world," says Bennett.

"As a result of the unique nature of this project, we anticipate that Phalaborwa can be brought into production far quicker than a traditional hard-rock rare earths mining project."